1. Field of the Invention
The present invention relates to a magnetic transfer apparatus for magnetically transferring information from a master medium bearing the information to a slave medium.
2. Description of the Prior Art
With regard to a magnetic recording medium, generally, a large-capacity and inexpensive medium capable of recording a greater deal of information has been preferred with an increase in the quantity of information. More preferably, one capable of reading a necessary spot within a short time, so-called a medium allowing high-speed access, has been in demand. As one example, a high-density flexible disc is known and, in order to realize a large capacity thereof, a so-called tracking servo technology plays a large role, which is adapted to accurately scan tracks with narrow widths by a magnetic head, and reproduce signals with a high S/N ratio. In one round of a disc, a servo signal for tracking, an address information signal, a reproducing clock signal and the like are recorded in a so-called preformat at given intervals.
The magnetic head is set to accurately travel on a track by reading the signals in the preformat and correcting its own position. Current preformats are created one by one, or one track by one track, by using a dedicated servo write apparatus.
However, such a servo write apparatus is expensive, and the creation of preformats takes a long time. Consequently, the creation step of preformats accounts for a large part of manufacturing costs, leading to a desire for cost reduction.
On the other hand, instead of creating a preformat one track by one track, another method of realization thereof by a magnetic transfer method has been proposed. As to the magnetic transfer method, disclosures have been made in, for examples, Japanese Unexamined Patent Publication Nos. 63(1988)-183623, 10(1998)-40544, 10(1998)-269566 and the like. Magnetic transfer is designed to transfer a magnetization pattern corresponding to information (e.g., servo signal) born on a master medium by applying a transfer magnetic field while the master medium is in a close contact with a slave medium. Static recording can be carried out without changing the relative positions of the master and slave media, accurate preformat recording can be carried out, and time necessary for the recording is extremely short.
To enhance the quality of transfer in the magnetic transfer, it is a large problem to bring the master and slave media into contact as close as possible without any gaps therebetween. If there is a close-contact failure, then an area of no magnetic transfer occurrence may be formed. If no magnetic transfer occurs, then there will be signals missing in the magnetic information transferred to the slave medium, thereby lowering signal quality. If a recorded signal is a servo signal, then a sufficient tracking function cannot be obtained, reducing reliability.
As one means of solving the foregoing problem, Japanese Unexamined Patent Publication No. 7(1995)-78337 discloses a technology for improving the close-contact property between the master and slave media by pressing the entire back side of the master medium with uniform pressure applied by press-contact means using an elastic body.
As another solution, Japanese Unexamined Patent Publication No. 11(1999)-161956 discloses a technology for improving the close-contact property by curving the center of the master medium into a convex shape protruding to the slave medium side, and bringing the master and slave media into close contact with each other while gradually flattening the master medium from the center to the outside by contact pressure while in close contact with the slave medium, thereby discharging air without any remaining in the close contact surface.
The foregoing solution is employed on the assumption that the master medium is basically flat. Depending on the forming method of a master medium or the like, it has been difficult to ensure sufficient flatness. Consequently, in such a master medium, a close-contact failure is not completely eliminated, bringing about insufficient close-contact property. Especially, in the case where magnetic transfer is simultaneously performed for the both surfaces of the slave medium by bringing the master media into close contact with both sides of the slave medium, the close contact cannot be obtained due to the difference in flatness between the master media on either side of the slave medium.
In addition, in the case of one, e.g., the foregoing conventional example, for obtaining flatness by deforming the master medium in the contact pressure stage, there is a possibility that friction in accordance with the deformation will be generated between the slave medium surface and the master medium, and damage will be given to a micro uneven pattern bearing the transfer information on the master medium surface, or the recording surface of the slave medium. In particular, if a flexible disc is used as a slave medium, deformation may possibly occur in the slave medium.
If an outer peripheral part or the like of the master medium is clamped when the master medium is fixed in a transfer position, a force is applied to a part of the master medium. Thus, the master medium may be deformed or destroyed. In addition, when the master medium is fixed by adhesive, it may be difficult to uniformly coat the adhesive. Such nonuniform coating of adhesive may damage the flatness of the master medium, as well as making it difficult to peel off the adhesive when the master medium is replaced by another. Consequently, the costly master medium may be damaged.
The present invention was made with the foregoing problems in mind, and it is an object of the invention to provide a magnetic transfer apparatus capable of enhancing the quality of a transfer signal by ensuring flatness of a master medium in magnetic transfer and improving the close-contact property between slave and master media.
In accordance with the present invention, a magnetic transfer apparatus is provided for performing magnetic transfer by bringing a master medium bearing transfer information and a slave medium subjected to the magnetic transfer into close contact with each other and applying a transfer magnetic field thereto. The magnetic transfer apparatus is characterized by having an adsorbing member having a flat surface for adsorbing and holding the backside of the master medium. In this case, the master medium is brought into close contact with the slave medium in an enhanced flatness state thereof.
The adsorbing member is constituted of a substance having an adsorbing surface, which has a predetermined flatness and a number of open suction holes alternatively a porous substance having an adsorbing surface, which has micro open suction holes therein. The suction holes on the adsorbing surface are connected through a suction passage to a vacuum pump for suction. The master medium is vacuum-adsorbed, and the flatness of the master medium is corrected along the adsorbing surface.
In the case of one-surface transfer, it is preferable that the master medium having had its flatness enhanced by adsorbing and holding its back side on the flat surface of the adsorbing member be brought into close contact with one surface of the slave medium, and an elastic body brought into contact with the opposite surface of the slave medium.
When the master medium has low rigidity, it is preferable that the intervals between the openings of the suction holes be reduced, and suction performed uniformly for an entire surface of the master medium through a number of suction holes. More preferably, the suction should be performed by the porous substance.
When the master medium is removed from the adsorbing member, it is preferable that the removal from the adsorbing surface be carried out by feeding pressurized air to the suction holes.
Preferably, an outer diameter of the master medium should be set larger than that of the recording area of the slave medium, and an inner diameter of the master medium should be set smaller than that of the slave medium.
When magnetic transfer is performed, it is preferable that the slave medium be subjected to initial DC magnetization beforehand in an in-plane tracking direction of the slave medium in the case of in-plane recording, or in a vertical direction to the slave medium in the case of vertical recording. Then, magnetic transfer is carried out by bringing the slave medium into close contact with the master medium, and applying a transfer magnetic field in a direction roughly reverse to the initial DC magnetization direction thereof in the tracking direction or the vertical direction.
As described above, according to the present invention, the adsorbing member is provided, capable of enhancing the flatness of the master medium by adsorbing the backside of the master medium brought into contact with the slave medium on a flat surface when magnetic transfer is performed in a state of close contact between the master and slave media. Hence, it is possible to secure close contact property with the slave medium on an entire surface thereof by enhancing the flatness of the master medium, and to prevent the occurrence of missing signals caused by a close contact failure. Then, transfer signal quality is enhanced to improve reliability.
No deformation occurs in the master medium when the slave and master media are pressed into contact with each other, and no friction occurs therebetween. Thus, it is possible to enhance the durability of the master medium, while preventing the occurrence of damage to the slave medium caused by the deformation or the like.
In the case of one-surface transfer, the master medium having a back side held by the adsorbing member is brought into close contact with one surface of the slave medium, and the elastic body is brought into close contact with the opposite surface of the slave medium. Accordingly, without any reduction in close-contact property caused by a difference in flatness between the master media on both sides of the slave medium as in the case when the master media are brought into close contact with both sides thereof, it is possible to further improve close contact property between the slave and master media.
When an adsorbing member made of a porous substance is used, an air suction structure can be simplified, and the suction holes on the surface can be micronized. Thus, it is possible to perform good suction and holding for the master medium having low rigidity while the flatness thereof is secured.
When the master medium is removed, it is possible to facilitate the removal of the master medium by feeding pressurized air to the suction holes.